Map fragment V2 in a Fragment

问题:

I am facing some issue"Null pointer Expcepttion at getmap()" in Google Map Fragments . I want to insert mapfragment in a fragment Please review the code and let know whether I am taking the right appraoch or not .. and let me know what exactly I need to do with my code to make it work

My Layout file :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent" 
  android:orientation="vertical"
  android:background="@drawable/bg2"
  android:weightSum="100">

<Button
    android:id="@+id/perx_button"
    android:layout_marginTop="70dip"
    android:layout_gravity="center"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/perx_card_btn" />

<fragment
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment" />

</LinearLayout>


public class PerxDetailedFragment extends SupportMapFragment {

  static final LatLng HAMBURG = new LatLng(53.558, 9.927);
  static final LatLng KIEL = new LatLng(53.551, 9.993);
 GoogleMap map;
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {

     FragmentTransaction ft = getFragmentManager().beginTransaction();

    map = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map))
            .getMap();

    SupportMapFragment fmap = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);

    if (fmap == null) {
        fmap = SupportMapFragment.newInstance();
        ft.add(R.id.map, fmap);
    }

    ft.commit();

    Marker hamburg = map.addMarker(new MarkerOptions().position(HAMBURG)
            .title("Hamburg"));
        Marker kiel = map.addMarker(new MarkerOptions()
            .position(KIEL)
            .title("Kiel")
            .snippet("Kiel is cool")
            .icon(BitmapDescriptorFactory
                .fromResource(R.drawable.ic_launcher)));

        // Move the camera instantly to hamburg with a zoom of 15.
        map.moveCamera(CameraUpdateFactory.newLatLngZoom(HAMBURG, 15));

        // Zoom in, animating the camera.
        map.animateCamera(CameraUpdateFactory.zoomTo(10), 2000, null);


     return inflater.inflate(R.layout.perx_detailed, null, false);
}
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);       


    }


}

回答1:

You need to inflate the layout first. The problem is you're doing that at the end of onCreateView, so the map fragment isn't there when you call findFragmentById.

Also, PerxDetailedFragment should extend Fragment, not SupportMapFragment.

public class PerxDetailedFragment extends Fragment {
    // ...

    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.perx_detailed, null, false);

        map = ((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map))
            .getMap();

        //...

        return v;
    }

回答2:

Remove all the fmap code:

SupportMapFragment fmap = (SupportMapFragment) getFragmentManager().findFragmentById(R.id.map);

if (fmap == null) {
    fmap = SupportMapFragment.newInstance();
    ft.add(R.id.map, fmap);
}

You already have an instance of the map saved as the "map" variable, so use that one.

回答3:

You need to extend SupportMapFragment

public class MapFragment extends SupportMapFragment{

GoogleMap mGoogleMap;
Context mContext;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    mContext=getActivity();
    View rootView = inflater.inflate(R.layout.fragment_home, container, false);
    initializeMap(rootView);
    return rootView;
}
void initializeMap(View rootView)
{
    if (mGoogleMap == null) {
        mGoogleMap=((SupportMapFragment) getFragmentManager().findFragmentById(R.id.map4)).getMap();
        // Getting Map for the SupportMapFragment
        mGoogleMap.setMyLocationEnabled(true);
            if (mGoogleMap == null) {
            Toast.makeText(getActivity().getApplicationContext(),"Sorry! unable to create maps", Toast.LENGTH_SHORT)
                    .show();
        } else {
            setMapDefualtProp();

        }
    }else
        setMapDefualtProp();
}

private void setMapDefualtProp() {
    mGoogleMap.setMyLocationEnabled(true);
    mGoogleMap.setTrafficEnabled(true);
    mGoogleMap.getUiSettings().setMyLocationButtonEnabled(true);
    mGoogleMap.getUiSettings().setRotateGesturesEnabled(true);
    mGoogleMap.getUiSettings().setCompassEnabled(true);
    mGoogleMap.getUiSettings().setZoomGesturesEnabled(true);
    mGoogleMap.getUiSettings().setZoomControlsEnabled(true);        
} 

}

回答4:

gMap = ((MapFragment) getActivity().getFragmentManager().findFragmentById(R.id.map)).getMap();